A power semiconductor device is such that a semiconductor element such as an IGBT (insulated gate bipolar transistor), MOSFET (metal-oxide-semiconductor field-effect transistor), IC chip, or LSI chip is die-bonded to an external terminal lead frame, after which an electrode of the semiconductor element and the external terminal are electrically connected by a wire or inner lead, and an input and output of signals from and to the exterior is carried out.
Also, a mold resin type of semiconductor device is such that a surface on a side of the lead frame on which the semiconductor element is mounted (a mounting surface), and a heat dissipating surface on a side opposite the mounting surface, are sealed by mold resin in a molding process. As a power semiconductor device includes a high-heat generating element in an interior thereof, high heat dissipation is required of the mold resin. For example, a semiconductor device presented in Patent Document 1 is such that the mounting surface of the lead frame is sealed by a low-stress resin used as a general integrated circuit mold resin, while the heat dissipating surface is sealed by a high-heat dissipating resin with thermal conductivity of 4 to 10 W/m·K.
Meanwhile, when sealing using two kinds of resin—a high-heat dissipating resin and a low-stress resin—as in Patent Document 1, there is a problem in that adhesion between the two resins is poor. In Patent Document 1, as a method of causing the high-heat dissipating resin and low-stress resin to adhere sufficiently, an outer peripheral end portion of the high-heat dissipating resin covering the heat dissipating surface of the lead frame is positioned inward of an outer peripheral end portion of the lead frame, and the high-heat dissipating resin in a semi-cured state is covered by the low-stress resin.